A bobbin winding machine designed as a cheese-producing textile machine is known, for example, from German Patent Publication DE 196 50 932 A1. Such so-called automatic cheese winders have a plurality of work stations designed as winding heads, which are usually arranged next to each other in the longitudinal extent of the bobbin winding machine. It is known to assign a separate work station computer to each winding head for operating, monitoring and controlling the bobbin winding machine. In this case, the individual work station computers are connected via a machine bus with a central control unit of the bobbin winding machine.
As a rule, such automatic cheese winders have a logistic device in the form of a bobbin and tube transport system. Delivery bobbins, e.g., so-called spinning cops, or respectively empty cop tubes circulate, standing upright on the arbors of transport disks, travel on this bobbin and tube transport system.
Such bobbin winding machines also have a service unit in the form of a cheese changer, which automatically services the work stations. The cheese changer transfers finished take-up bobbins from the creel of the work station to a transport device which extends the length of the machine to convey the cheeses to a transfer station arranged at the end of the machine. The service unit subsequently inserts a fresh empty tube into the creel of the respective work station.
During the rewinding of the yarn from a delivery bobbin to a take-up bobbin, it is known to monitor the running yarn, e.g., by means of a yarn tension sensor, and to keep the yarn tension at a predetermined level by means of a yarn tensioner. This means that an essentially constant yarn tension is set by means of the yarn tensioner in order to assure the uniform winding of the yarn on the take-up bobbin in this manner.
It is known from German Patent Publication DE 41 29 803 A1 to detect the actual yarn tension of the running yarn by means of a yarn tension sensor. A control signal for the yarn tensioner is made available by means of a yarn tension measurement performed by this yarn tension sensor on the running yarn which, in accordance with the control signal, then exerts a more or less large braking effect on the running yarn. In this manner, it is assured that the yarn is wound at a defined tension on the take-up bobbin.
It is furthermore known in the course of the rewinding process to guide the running yarn through a so-called yarn cleaner. This yarn cleaner traces the running yarn to detect irregularities, for example thickened or thin places. If such irregularities are detected, a yarn cut is triggered by the yarn cleaner. In the process the running yarn is cut below the faulty place, creating two cut yarn ends which may be referred to as a bottom yarn and a top yarn. The top yarn having the faulty place initially runs up on the cheese, since the latter cannot be abruptly braked to a stop because of its relatively great centrifugal mass.
With a controlled yarn cleaning cut, the bottom yarn is usually held in the yarn tensioner and can be transferred by means of a so-called gripper tube into a splicing device, wherein the end of the bottom yarn is connected with the end of the top yarn, which is retrieved from the cheese surface by means of a pivotably seated suction nozzle.
It is moreover known to equip the bobbin winding machines with a so-called bottom yarn sensor, which detects the presence of the bottom yarn, since the presence of the bottom yarn is absolutely necessary for the successful performance of a yarn connection.
As already explained above, in the course of an intended yarn cut because of a detected irregularity in the yarn, the bottom yarn as a rule is held by the yarn tensioner so that the bottom yarn sensor thereof, which is arranged upstream as viewed in the traveling direction of the yarn, can detect the presence of a bottom yarn.
However, operational states can also occur in the course of the operation of the bobbin winding machine which are caused by a yarn break or the exhaustion of the delivery bobbin, for example. In case of a yarn break, a search for the top yarn and the bottom yarn is performed by the splicing device, and they are automatically reconnected with each other analogously to the connection of the bottom yarn and the top yarn in case of an intended yarn cut. If the delivery bobbin has run out, or if the yarn breaks below the yarn tensioner, the absence of a bottom yarn in detected by the bottom yarn sensor. In such a case, a delivery bobbin changing device is automatically activated by the work station computer of the winding head, which makes sure that the empty cop tube or the spinning cop (as the case may be), which can no longer be unwound because of the lack of a bottom yarn, is exchanged for a fresh delivery bobbin.
It is also possible for hook formations of the yarn and/or loop formations to occur at the delivery bobbin, in particular in connection with a yarn break above the yarn tensioner. As a result, although the bottom yarn sensor detects the presence of a bottom yarn, these hooked yarns or loops can prevent the respective winding head from operating automatically in spite of several repetitions of the yarn connecting process.
In case of a hooked yarn and/or loop formation at the delivery bobbin, a yarn break will immediately occur again after the restart of the winding head. In this connection, it is disadvantageous, among other things, that a loss of time occurs because of the repeated connecting and breaking of the yarn, which results in a loss of productivity of the respective winding head.